1. Field of the Invention
This invention relates to plastic bags, and more particularly to a pack of T-shirt bags, merchandise bags, trash bags, and the like made preferably of polyolefins, and method of manufacturing same, which can be used with a variety of different sized bagging racks.
2. Description of the Prior Art
Since the mid-1980's, the use of plastic shopping bags has grown dramatically due to the great advantage plastic bags have over bags made of other materials, such as paper. Plastic bags are typically made of low or high density polyethylene (LDPE and HDPE, respectively), but can be made of any of the polyolefins. LDPE and HDPE bags are stronger, lighter and much more compact than paper bags when stacked, saving valuable storage space at the merchants' checkout counter and storage areas. These attributes also make these bags less expensive to transport. LDPE and HDPE bags can be manufactured and sold much less expensively than competing paper bags, making them the bags of choice for merchants. LDPE and HDPE bags are also environmentally friendly since they require 70 percent less energy to manufacture than competing paper bags and are readily recyclable, and when not recycled, are non-toxic when incinerated or disposed of in landfills.
Many groceries stores and other merchants now use a style of plastic bag to bag groceries called T-shirt bags. T-shirt bags are pleated bags which are closed, by heat sealing, at a bottom edge, and have a pair of integral handles extending upwardly to define an open mouth of the bag therebetween. The handles allow the grocery loaded bags to be more easily carried. Because high density polyethylene (HDPE) has a greater resistance to stretching and deformation, HDPE is generally used for making T-shirt bags, although LDPE and other polyolefins can also be used. T-shirt bags are normally provided in packs of aligned bags and these packs of bags are generally carried on a bagging racks for easy loading of the bags.
T-shirt bags are generally manufactured by the following process. A continuous tube of HDPE, LDPE, LHDPE, or some combination of these and other plastic materials having the desired color, thickness, diameter, and physical qualities such as tensile strength, stretch and tear resistance, is formed on a extruding machine. The continuous plastic tube is then passed over rollers to roll the continuous plastic tube onto a spool. Depending on whether or not the bags to be formed from the continuous tube of HDPE will be printed on one or both sides, the newly formed continuous tube may be subjected to corona surface treatment, wherein the side or sides of the continuous flattened tube of plastic which are to be later printed will be passed by high voltage corona discharge electrodes. Corona surface treatment affects electrical and chemical changes on the plastic's outer surface to prepare that surface of the bag for printing. Corona surface treatment also contributes to creating frangible pressure bonding and the reliable self-opening operation of the instant plastic bag pack system of the invention.
After being corona surface treated and rolled, the roll of continuous plastic tube is typically pleated on two sides in order to double from two to four the number of layers of plastic material on two side regions of the pleated roll. (The handles of the assembled bags are latter cut into this double thick side regions for added strength). A bagging machine is used to heat seam close and cut individual the pleated tubes into sections having a desired length, with the cut sections of the pleated tube at top and bottom edges forming closed and flattened pleated bags of a desired length and width (sometimes referred to as "pillowcases"), with the pleated sides being at both sides of the flatted pleated bags. Further downstream of the heat seaming and cutting step, the bags are stacked in aligned piles. Thereafter, a hydraulic die or other cutting method or tool is utilized to remove material at the stacked bags' top portion to form the handles and a central tab portion with a central tab slit for support of the pack of bags on a hook of a bagging neck and a tearing line below the central tab slit. Usually a heat weld is utilized to hold the stack of central tabs together, thus forming a pack of bags. Each handle will comprise four layers of material since they are cut out from the pleated side portions of the bag. This not only makes the handles stronger, but also thicker, and more comfortable to hold.
Despite the many advantages HDPE T-shirt bags have over paper bags, unlike thicker and stiffer paper bags with a discreet flat bottom, they are not self-standing. This is due to their relatively thin and flexible material. In grocery stores settings, where quick and easy loading of bags is desirable, T-shirt bags are provided in stacks or packs which are generally supported on a bagging rack as merchandise is loaded into the bags to overcome the lack of self-standing ability.
There are several popular styles of T-shirt bags available in packs of bags and bagging racks for use therewith, some main types of which will be discussed. In one type of pack of T-shirt bags and bagging racks used therewith, the bagging rack has a support base, a wire rear wall with a tab receiving hook, and two wire arms extending forwardly over the base. In the center top portion of the arms, the wire is formed so as to have a section which will spread and hold apart the handles of T-shirt bags engaged therewith to open up the mouth of the T-shirt bag. The pack of T-shirt bags used with these styles of bagging racks consists of a stack of overlapped and aligned bags which have a lower bag portion with two handles extending upwardly at both sides of the mouth of the bag. A central tab portion is provided on the mouth of the bags between the two handles, and the central tab portions of the pack of bags are heat-sealed together. The heat sealed central tabs thus form a stack or book of central tabs and have a central tab slit formed therethrough. The central tab slit is engaged with the tab receiving hook on the rear wall of the bagging rack, and the book of central tabs will remain engaged therewith, even after individual bags are removed. Below the central tab slit a tearing slit is provided which traverses almost the entire distance of the central tabs except for a small distance at both sides of the central tab portion. The tearing slit allows the individual bags to be torn off the pack of bags as they are needed, and looped onto the bagging rack.
A second major type of pack of T-shirt bag, and bagging rack designed to be used therewith, are disclosed in U.S. Pat. No. RE 33,264 to Baxley, et al. Another version of this style of bagging rack is disclosed in U.S. Pat. No. 4,840,336 to Stroh, et al. Both of these bagging racks have a bottom support base and a rear wire wall with a tab receiving hook located thereon. However, to open up each individual bag for loading, instead of looping the handles of the bags over the top of the support arm one at a time, as is done with the first type of pack of bags and rack, these racks have two handle support rods extending forwardly from the rear wire wall of the rack. The pack of T-shirt bags used with these styles of racks are similar to those used with the first type of rack, except that aligned, inverted horseshoe-shaped aperture s are formed on each handle of the pack of bags, through which pass the handle support rods of the bagging rack. In these prior art inverted horseshoe-shaped apertures, the cut ends are turned inwardly and upwardly. The theory behind the prior art inverted horseshoe-shaped handle aperture cut is that any slit or cut in a bag is a potential tear and rip initiation point, which can damage the integrity of the bag. By using an inverted, horseshoe shaped handle aperture cut with turned up and in ends, any potential tearing at the ends will tend to be propagated inwardly and upwardly, into the flap formed by the cut, which it is harmless. While inverted horseshoe shaped handle apertures do accomplish the intended purpose, they reduce the effective, continuous width of the handles and can somewhat weaken the handles. The longer the horseshoe, the weaker the bag handles become.
Despite the attempts to overcome the problems associated with these presently available T-shirt bags, there continues to remain a need for an improved pack of T-shirt bags which can be used with a variety of bagging racks, which is easily manufactured, and which is strong.